Family Mold
A multiple cavity mold which produces
non-identical parts simultaneously.
Feed Section
The section of the screw just under and
slightly forward of the feed hopper.
Fill Pattern
The contour the melt takes sequentially as it
fills the cavity. The mold should fill with a straight flow
front with no changes in direction throughout filling.
Mold-filling analysis software can be used to predict these
filling patterns.
Fill Pressure
The pressure required to fill the cavity.
Filler
A relatively inert substance added to a plastic
compound to reduce its cost and/or to improve physical
properties, particularly hardness, stiffness and impact
strength.
Filler
Fillers are generally inert materials characterized by
a low aspect ratio (4D). They are commonly used as extenders;
fillers do in fact improve certain material properties such as
wear, resistance, electrical properties, modulus values, HDT
and others.
Film
Films are distinguished from sheets in the plastics
industry only according to their thickness. In general, films
have thicknesses no greater than .030".
Finish
The surface texture of a finished article.
Fisheyes
Describes a very small void which has not blended
completely with the surrounding material. Usually caused by a
minute quantity of silicone, oil or other surface contaminate
on the surface of the substrate.
Flame Resistance
Deprecated term: not recommended, owing to
risk of misunderstanding.
Flame Retardant
Having the ability to resist combustion (A
flame retardant plastic is considered to be one that will not
continue to burn or glow after the source of ignition has been
removed.) Retardant, or retarder: a substance used in small
proportion to reduce the reaction rate of a chemical system.
Flame retardant: a substance added, or treatment applied, to a
material in order to suppress, significantly reduce or delay
the propagation of flame. Flame retardants may be added to
plastics materials (external flame retardants) or incorporated
as chemical groups in the base polymer during the
polymerization process (internal flame retardants). Flame
retardance is the property of a material, either inherent or
by virtue of a substance added or a treatment applied, to
suppress significantly, reduce or delay the propagation of
flame. Flame retarded: treated with a flame retardant. fire
retardant: a substance added, or treatment applied, to a
material in order to suppress, significantly reduce or delay
the combustion of the material.
Flash
Resin that is forced out of the mold cavity area and
onto the parting line or into the vents of the mold. A very
thin film of cured resin attached to the molded part.
Flash Pockets
Flash pockets provide relief areas outside the
pinch-offs to limit the amount of compression for mold
closing. The flash pockets are sometimes referred to as gutter
or relief areas. Ideally, flash pockets will be deep enough to
lessen the compression of the flash material, while providing
enough surface contact to cool the flashed material.
Flashpoint
The temperature at which solvents volatilize
sufficiently to produce a flammable mixture.
Flow
The ability of the molten resin to move or travel during
injection. Flow can be influenced by temperature, part design,
process conditions and tool design.
Flow Balancing
Modifying flow paths, particularly runner
sections, so that all flow paths within a mold fill in equal
time with equal pressure.
Flow Leader
A small area in the mold (usually no more than
0.200" to 0.300" wide) which locally thickens the wall to
allow material to flow into outer areas more smoothly. A
molders "trick" to get a few more inches of flow from the
material. Usually not designed in the initial stage of tool
construction. Use should be based on experience or qualified
molder inputs. Also known as a flow rib.
Flow Pattern
The contour the melt takes sequentially as it
fills the cavity. The mold should fill with a straight flow
front with no changes in direction throughout filling.
Mold-filling analysis software can be used to predict these
flow patterns.
Flow Rate
The volume of material passing a fixed point per
unit time.
Flow Restrictor
A small area in the mold which usually thins
the wall to stall the flow of resin to select areas of the
mold. Used to steer the material in another direction
Foaming
Foaming is the process of producing a cellular
plastic by using foaming agents. A foaming agent is a material
mixed with or dissolved in a plastic to make it foam. It
includes expanding agents that produce gas on heating – such
as easily volatile solvents – or chemical blowing agents that
produce gas by thermal decomposition. Weight reduction is the
percent volume of a foamed part which contains gas instead of
resin. To get 10% weight reduction, the mold is filled 90%,
then allowed to "foam" and fill that last 10%. Since only 90%
of the volume is resin, the part weighs 10% less than a solid
part of the same dimensions would. High weight reductions
result in reduced material properties when compared to low
weight reductions.
Foaming Agent
Any substance which alone or in combination with
other substances is capable or producing a cellular structure
in a plastic mass.
Forming
A general term encompassing processes in which the
shape of plastic pieces such as sheets, rods or tubes is
changed to a desired configuration.
Gate
In injection molding, the channel through which the
molten resin flows from the runner into the cavity.
Gate Blush
A blemish or disturbance in the gate area of an
injection molded article.
Hardness
The hardness of a material can be measured by its
resistance to scratching or to indentation. Mostly used
hardness tests involve the determination of the material
resistance to indentation under standardized conditions. A
hard indenter of standard shape is pressed into the surface of
the material under a specified load. The resulting area of
indentation or the depth of indentation is measured and
assigned a numerical value. Various methods can be used. For
plastics, the most widely used methods are Ball hardness,
Rockwell and Shore methods.
Hold Pressure
The applied hydraulic injection pressure
maintained after the completion of mold filling. Also referred
to as secondary pressure.
Homopolymer
Homopolymers are polymers which are made up of one
single repeated basic unit or (mono)mer.
Hopper
The device above the machine barrel used to store the
resin pellets.
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